Volute Mechanism of a Centrifugal Fan

ABSTRACT

A centrifugal fan, which comprises an air flow chamber disposed inside the volute, an air outlet attached to the air flow chamber and a volute tongue attached to the air outlet; wherein, the volute tongue comprises a tongue body and an enclosed noise-reducing chamber, the tongue body has a plurality of holes for allowing the air flow from the air flow chamber into the noise-reducing chamber; and a sound collector capable of detecting the intensity of noise and a sounder capable of playing sound are disposed in the noise-reducing chamber. The noise is actively reduced and the secondary discharge of the backflow gas is realized, so that the gas backflow is reduced and the vortex is eliminated.

RELATE APPLICATIONS

This application claims benefit to Chinese Patent Application for a volute for a centrifugal fan, 201810418925.6, filed on May 4, 2018. The specification of the application is incorporated here by this reference.

FIELD OF THE INVENTION

The present invention relates to the technical field of range hoods, and in particular to a volute for a centrifugal fan.

DESCRIPTION OF THE PRIOR ART

For domestic range hoods, air suction and air exhaust are performed by multi-blade centrifugal fans. A fan generally consists of a volute, a motor, an impeller and the like. A tongue-like protrusion in the volute is called a volute tongue which mainly functions to isolate the flowing gas and prevent the gas from circulating in the volute. Due to the high pressure and complicated flow of gas in the vicinity of the volute tongue, the flow noise and rotation noise generated in the vicinity of the volute tongue are the main noise sources of the centrifugal fan. Therefore, reducing the noise in the vicinity of the volute tongue can significantly reduce the noise of the range hood.

A Chinese Patent application CN105526193A (Application No.: CN201610111243.1) entitled FAN VOLUTE FOR RANGE HOOD, disclosed a volute of a fan, which includes a volute tongue, wherein the volute tongue includes an inner wall of the volute tongue; the volute tongue forms an enclosed cavity; at least one longitudinal partition plate is arranged within the cavity in an axial direction of the volute, and a plurality of radial partition plates are arranged within the cavity in a direction perpendicular to the axis of the volute; the cavity is divided into a plurality of independent enclosed silence cavities by the longitudinal partition plate and the radial partition plates; and, a hole is formed on the inner wall of the volute tongue corresponding to each silence cavity. In the above structure, the cavity in the volute tongue is divided into a plurality of independent small enclosed cavities, and a Helmholtz resonator is formed by the small cavities and the holes formed on the corresponding sidewall. In accordance with the Helmholtz resonance principle, after the sound is transmitted, the sound waves close to the inherent frequency of the resonator resonate with the resonator. During vibration, air columns in the cavity rub against the inner wall of the cavity to consume the sound energy, realizing sound adsorption and noise reduction.

In the volute with the above structure, by providing the silence cavities, the noise of the fan is reduced to a certain extent. However, due to the small space at the volute tongue, it is difficult to completely discharge the gas at one time, and the residual gas is easy to flow back and form vortex. Consequently, the fan efficiency is reduced, and the vortex noise is generated, so that the fan still has high noise.

SUMMARY OF THE INVENTION

A technical problem to be solved by the present invention is, in view of the prior art, to provide a volute for a centrifugal fan, which reduces the fan noise and improves the fan efficiency by eliminating vortex through active noise reduction.

To solve the above technical problem, the volute for a centrifugal fan, comprises an air flow chamber disposed inside the volute, an air outlet attached to the air flow chamber and a volute tongue attached to the air outlet; wherein, the volute tongue comprises a tongue body and an enclosed noise-reducing chamber, the tongue body has a plurality of holes for allowing the air flow from the air flow chamber into the noise-reducing chamber; and a sound collector capable of detecting the intensity of noise and a speaker capable of playing sound are disposed in the noise-reducing chamber.

Preferably, the tongue body is in L-shaped and has a vertical portion and a transverse portion; the volute tongue further comprises two side plates respectively disposed on each side of the tongue body, and a rear plate having a top and a bottom; the top and the bottom of the rear plate are respectively connected to the vertical portion and the transverse portion of the tongue body, and the noise-reducing chamber is enclosed by the two side plates, the rear plate and the L-shaped tongue body; the plurality of holes are defined on the vertical portion of the tongue body, and the sound collector and the speaker both have a front side which faces the rear plate. This structure is advantageous for realizing better noise cancellation.

As an improvement, a L-shaped air-guiding plate having a vertical portion and a transverse portion is disposed adjacent to the tongue body, the two side plates both extend to the air-guiding plate; the vertical portion of the air-guiding plate and the vertical portion of the tongue body are separated with an interval, which forms a narrow air-guiding passage, the top of the air-guiding passage is in communication with the air outlet; and the transverse portion of the air-guiding plate is connected to the transverse portion of the tongue body; an air-guiding chamber is enclosed by the two side plates, the bottom of the vertical portion of the air-guiding plate, the transverse portion of the air-guiding plate and the vertical portion of the tongue body, the air-guiding chamber is in communication with the air-guiding passage; an opening for allowing the air flow from the air flow chamber to enter into the air-guiding chamber is disposed on the transverse portion of the air-guiding plate. The airflow flows from the air flow chamber inside the volute through the air-guiding chamber and the air-guiding passage, some of the airflow flows directly from the top of the air-guiding passage to the air outlet after acceleration, and some of the airflow enters the noise reduction chamber from the holes. This structure can effectively reduce gas backflow and eliminate vortex.

As a further improvement, a movable air-guiding block with a first end and a second end for removably covering the opening is disposed inside the air-guiding chamber, and an adjustment component for controlling the air-guiding block to cover or uncover according to the intensity of the air flow is disposed on the volute tongue. With such a structure, when the air volume is relatively small, the adjustment component does not work, and the conventional structure of the volute tongue can satisfy the requirements; and, when the air volume is relatively large, the adjustment component drives, under the impact of the air flow, the air-guiding block to move so as to open the opening, so that the function of eliminating vortex and reducing gas backflow is realized.

Preferably, the adjustment component comprises two pairs of connecting arms, pins and elastic members, each of the elastic members having a first end and a second end; each connecting arm is connected to the first end of the air-guiding block and rotatably connected to the side plate through one pin; the air-guiding block rotates around the pins, and floats upwardly under the impact of the air flow so as to uncover the opening, the second end of the air-guiding block is a free movable end; and the elastic member pushes the air-guiding block to cover the opening. The elastic coefficient of the elastic member can be set according to specific performance parameters such as the air pressure of the fan system and the flow. Thus, it is determined, according to the air volume, whether the opening is to be closed, to maintain the low noise of the fan.

For assembly convenience, preferably, the elastic member is a spring, the first end and the second end of the elastic member respectively resist against the top of the corresponding connecting arm and the air-guiding plate.

Preferably, the air-guiding plate has a resisting plane arranged perpendicularly to the spring and is formed on the inner wall of the air-guiding plate above the elastic member, and the second end of the elastic member rests against the resisting plane; and, a recess for receiving the first end of the spring is formed on the top surface of each connecting arm.

Preferably, the vertical portion of the tongue body has a thickness between 1.5 mm and 2 mm, and the holes have a diameter between 2.3 mm and 3.2 mm.

In the above solutions, the volute further comprises an annular volute wall with a first end and a second end, the volute tongue is connected to the first end of the annular volute wall; in the tongue body, the transverse portion is defined as a first cambered section, the vertical portion is defined as a first planar section, and the connecting portion between the transverse portion and the vertical portion is defined as a second cambered section; the first cambered section is arranged closer to an impeller of the centrifugal fan compared to the first planar section, and the bottom surface of the first cambered section serves as a first air-guiding surface of the centrifugal fan; the first planar section is adjacent to the air outlet of the volute, and the outer surface of the first planar section serves as a second air-guiding surface of the centrifugal fan.

For ease of connection, preferably, the volute further comprises a front cover plate and a rear cover plate, the annular volute wall is connected between the front cover plate and the rear cover plate; an edge of vertical portion is connected to an inner wall of the front cover plate and the rear cover plate, and an edge of the transverse portion is connected to the first end of the annular volute wall and sealed with each other by silicone.

Preferably, the volute further comprises an annular volute wall with a first end and a second end, the volute tongue is connected to the first end of the annular volute wall; in the tongue body, the transverse portion is defined as a first cambered section, the vertical portion is defined as an upper second planar section and a lower the third cambered section; in the air-guiding plate, the vertical portion is defined as a first planar section, and the connecting portion between the transverse portion and the vertical portion is defined as a second cambered section; the second planar section is arranged closer to the first planar section compared to the first cambered section, the third cambered section is arched toward the air-guiding plate, and is smooth connected to the first cambered section; the first cambered section is arranged close to an impeller of the centrifugal fan, and the bottom surface of the first cambered section serves as a first air-guiding surface of the centrifugal fan; the first planar section is adjacent to the air outlet of the volute, and the outer surface of the first planar section serves as a second air-guiding surface of the centrifugal fan.

Preferably, the interval at the top of the air-guiding passage is smaller than that of the bottom of the air-guiding passage. With the above structure, an approximately 6-shaped chamber is formed by the air-guiding chamber and the long and narrow air-guiding passage, so that good effects of guiding flow and eliminating vortex are achieved by the chamber with this shape.

Preferably, the bottom surface of the air-guiding block is a cambered surface protruding downward, and correspondingly, each wall of the opening on the transverse portion is a cambered surface matching with the bottom surface of the air-guiding block.

Preferably, the top surface of the air-guiding block is a chambered surface protruding upward, the radian of the top surface is greater than that of bottom surface of the air-guiding block, and the connecting portion between the top surface and the bottom surface is smooth. With the above structure, the resistance to the air flow from the air-guiding block can be reduced.

Compared with the prior art, the present invention has the following advantages. Since the volute tongue in the present invention has a noise-reducing chamber, during the use of the centrifugal fan, a gas flow can enter the noise-reducing chamber through the holes of the tongue body. The sound collector in the chamber can acquire a noise signal and transmit it to a controller, and the controller calculates a noise-reduced audio signal according to the acquired signal and then controls the speaker to play the corresponding reduced noise according to the noise-reduced audio signal, so that the active noise reduction is achieved.

In addition, the volute tongue of the present invention, the vortex at the volute tongue is eliminated, therefore the fan noise is reduced and the fan efficiency is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a volute for a centrifugal fan according to Embodiment 1 of the present invention (when an impeller is assembled);

FIG. 2 is a sectional view of Embodiment 1 of the present invention;

FIG. 3 is a perspective view of a volute tongue according to Embodiment 1 of the present invention, showing the structure of the volute tongue;

FIG. 4 is a sectional view of a volute for a centrifugal fan according to Embodiment 2 of the present invention (when an impeller is assembled);

FIG. 5 is a sectional view of a volute tongue according to Embodiment 2 of the present invention (when a air-guiding block is omitted);

FIG. 6 is a perspective view of an adjustment component and the air-guiding block according to Embodiment 2 of the present invention; and

FIG. 7 is a sectional view of the volute tongue according to Embodiment 2 of the present invention (when the adjustment component is disposed inside the volute tongue).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

To enable a further understanding of the present invention content of the invention herein, refer to the detailed description of the invention and the accompanying drawings below:

Embodiment 1

FIGS. 1-3 show a centrifugal fan with a volute according to Embodiment 1 of the present invention. The volute according to Embodiment 1 comprises a volute tongue 1, a front cover plate 2, a rear cover plate 3, an annular volute wall 4 with a first end 41 and a second end 42, a sound collector and a speaker 6; wherein, the annular volute wall 4 is connected between the front cover plate 2 and the rear cover plate 3; an air flow chamber 4 a disposed inside the volute is formed by the front cover plate 2, the rear cover plate 3 and the annular volute wall 4; the volute tongue 1 is connected to the first end 41 of the annular volute wall 4; an air outlet 40 is enclosed by the second end 42 of the annular volute wall 4, the sidewall of the volute tongue 1 opposite to the second end 42 of the annular volute wall 4, the front cover plate 2 and the rear cover plate 3.

In this embodiment, the volute tongue 1 has a tongue body 11 in L-shaped with a vertical portion 11 a and a transverse portion 11 b, two side plates 12 respectively disposed on each side of the tongue body 11, and a rear plate 13 having a top and a bottom; wherein the top and the bottom of the rear plate 13 are respectively connected to the vertical portion 11 a and the transverse portion 11 b of the tongue body 11, and a noise-reducing chamber 10 is enclosed by the two side plates 12, the rear plate 13 and the L-shaped tongue body 11; a plurality of holes 110 are defined on the vertical portion 11 a of the tongue body 11, the plurality of holes 110 connect the air flow chamber 4 a and the noise-reducing chamber 10, and allow the air flow from the air flow chamber 4 a into the noise-reducing chamber 10; and the sound collector 5 and the speaker 6 both have a front side which faces the rear plate 13; a sound collector 5 capable of detecting the intensity of noise and a speaker 6 capable of playing sound are disposed in the noise-reducing chamber 10 and both have a front side which faces the rear plate 13, it is advantageous for realizing better noise cancellation.

A controller (not shown in figures) is disposed on the volute, which is connected with the electric signals of the sound collector 5 and the speaker 6. The noise signal collected by the sound collector 5 is transmitted to the controller. The controller calculates the required noise reduction frequency signal according to the noise signal, and controls the speaker 6 to play the corresponding reduced noise, so as to achieve the effect of noise cancellation

Wherein, in the tongue body 11, the transverse portion 11 b is defined as a first cambered section 111, the vertical portion 11 a is defined as a first planar section 113, and the connecting portion between the transverse portion 11 b and the vertical portion 11 a is defined as a second cambered section 112; the first cambered section 111 is arranged closer to an impeller of the centrifugal fan compared to the first planar section 113, and the bottom surface of the first cambered section 111 serves as a first air-guiding surface of the centrifugal fan; the first planar section 113 is adjacent to the air outlet 40 of the volute, and the outer surface of the first planar section 113 serves as a second air-guiding surface of the centrifugal fan; the second cambered section 112 is connected between the first cambered section 111 and the first planar section 113. In this embodiment, an edge of vertical portion 11 a is connected to an inner wall of the front cover plate 2 and the rear cover plate 3 by screws, and a lower edge of the volute tongue 1 is connected to the first end 41 of the annular volute wall 4 and sealed with each other by silicone.

Embodiment 2

FIGS. 1, 4-6 show a centrifugal fan of Embodiment 2 with the volute of the present invention. This embodiment differs from Embodiment 1 in that: in this embodiment, volute tongue 1 not only has a tongue body 11, two side plates 12 and a rear plate 13, but also has a L-shaped air-guiding plate 14 having a vertical portion 14 a and a transverse portion 14 b disposed adjacent to the tongue body 11.

The vertical portion 14 a of the air-guiding plate 14 and the vertical portion 11 a of the tongue body 11 are separated with an interval, which forms a narrow air-guiding passage 151, a top 152 of the air-guiding passage 151 is in communication with the air outlet 40; the top 152 is disposed between the vertical portion 14 a of the air-guiding plate 14 and the vertical portion 11 a of the tongue body 11; and the transverse portion 14 b of the air-guiding plate 14 is connected to the transverse portion 11 b of the tongue body 11.

An air-guiding chamber 15 is enclosed by the two side plates 12, the bottom of the vertical portion 14 a of the air-guiding plate 14, the transverse portion 14 b of the air-guiding plate 14 and the vertical portion 11 a of the tongue body 11, the air-guiding chamber 15 is in communication with the air-guiding passage 151.

In this embodiment, the air-guiding chamber 15 and the narrow air-guiding passage 151 form a cavity of roughly “6” shape, which has a good effect of diversion and eddy breaking.

And an opening 14 c for allowing the air flow from the air flow chamber 4 a to enter into the air-guiding chamber 15 is disposed on the transverse portion 14 b of the air-guiding plate 14. It is clear that, except the noise-reducing chamber, the air-guiding chamber 15 and the air-guiding passage 151 are added in this embodiment.

The long and narrow air-guiding passage 151 is formed between an upper second planar section 131′ of the rear plate 13 and a first planar section 113′ of the volute tongue 11, and the interval at the top of the air-guiding passage 151 is smaller than that of the bottom of the air-guiding passage 151. The air-guiding chamber 15 is enclosed by a lower portion of the rear plate 13 and an inner wall of the noise-reducing chamber 10.

In the tongue body 11, the transverse portion 11 b is defined as a first cambered section 111′, the vertical portion 11 a is defined as an upper second planar section 131′ and a lower the third cambered section 132′; in the air-guiding plate 14, the vertical portion 14 a is defined as a first planar section 113′, and the connecting portion between the transverse portion 14 b and the vertical portion 14 a is defined as a second cambered section 112′; the second planar section 131′ is arranged closer to the first planar section 113′ compared to the first cambered section 111′, the third cambered section 132′ is arched toward the air-guiding plate 14, and is smooth connected to the first cambered section 111′; the first cambered section 111′ is arranged close to an impeller of the centrifugal fan, and the bottom surface of the first cambered section 111′ serves as a first air-guiding surface of the centrifugal fan; the first planar section 113′ is adjacent to the air outlet 40 of the volute, and the outer surface of the first planar section 113′ serves as a second air-guiding surface of the centrifugal fan.

In this Embodiment, the vertical portion 11 a of the tongue body 11 has a thickness between 1.5 mm and 2 mm, and the holes 110 have a diameter between 2.3 mm and 3.2 mm, preferably 2.7 mm.

A movable air-guiding block 7 with a first end 7 a and a second end 7 b for removably covering the opening 14 c is disposed inside the air-guiding chamber 15; the bottom surface 71 of the air-guiding block 7 is a first cambered surface 101 protruding downward, and correspondingly, each wall of the opening 14 c on the transverse portion 14 b is a cambered surface 14 d matching with the first cambered surface 101; the top surface 72 of the air-guiding block 7 is a second chambered surface 102 protruding upward, the radian of the second chambered surface 102 is greater than that of first cambered surface 101, and the connecting portion between the first cambered surface 101 and the second chambered surface 102 is smooth. With the above structure, the resistance to the air flow from the air-guiding block 7 can be reduced.

In this Embodiment, an adjustment component 16 for controlling the air-guiding block 7 to cover or uncover according to the intensity of the air flow is disposed on the volute tongue 1; the adjustment component 16 comprises two pairs of connecting arms 161, pins 162 and elastic members 163, each of the elastic members having a first end 163 a and a second end 163 b; each connecting arm 161 is connected to the first end 7 a of the air-guiding block 7 and rotatably connected to the side plate 12 through one pin 162; the air-guiding block 7 rotates around the pins 162, and floats upwardly under the impact of the air flow so as to uncover the opening 14 c, the second end of the air-guiding block 7 is a free movable end; and the elastic member 163 pushes the air-guiding block 7 to cover the opening 14 c.

The elastic coefficient of the elastic member 163 can be set according to specific performance parameters such as the air pressure of the fan system and the flow. The first end 163 a and the second end 163 b of the elastic member 163 respectively resist against the top of the corresponding connecting arm 161 and the air-guiding plate 14. the air-guiding plate 14 has a resisting plane 14 e arranged perpendicularly to the spring and is formed on the inner wall of the air-guiding plate 14 above the elastic member 163, and the second end 163 b of the elastic member 163 rests against the resisting plane 14 e; and, a recess 1611 for receiving the first end 163 a of the spring is formed on the top surface of each connecting arm 161.

When in use of the volute in this embodiment, when the flow of the fan is small and the noise is low, the opening 14 c is closed by the air-guiding block 7 under the force of the elastic member 163; and, when the flow of the fan is large, the backflow of gas at the volute tongue 1 is increased, and the gas flow impacts the air-guiding block 7 to overcome the resistance of the elastic member 163 and then float upward, so as to open the opening 14 c. In this case, part of gas in the air flow chamber 4 a enters the air-guiding chamber 15 through the opening 14 c. The part of gas entering the air-guiding chamber 15 is directly accelerated by the long and narrow air-guiding passage 151 and then discharged from the top 152 of the air-guiding passage 151 and the air outlet 40 after accelerated; and, the other part of gas enters the noise-reducing chamber 10 through the holes 110. At this time, a noise signal acquired by the sound collector 5 is transmitted to the controller, and the controller calculates the required noise-reduced audio signal according to the noise signal and controls the speaker 6 to play the corresponding reduced noise, so that the noise reduction is realized. With such a structure, the noise is reduced in an active noise reduction manner, and the secondary discharge of the backflow gas is realized, so that the gas backflow is reduced and the vortex is eliminated. Accordingly, the fan noise is reduced and the fan efficiency is improved. 

1. A volute for a centrifugal fan, comprising an air flow chamber disposed inside the volute, an air outlet attached to the air flow chamber and a volute tongue attached to the air outlet; wherein, the volute tongue comprises a tongue body and an enclosed noise-reducing chamber, the tongue body has a plurality of holes for allowing the air flow from the air flow chamber into the noise-reducing chamber; and a sound collector capable of detecting the intensity of noise and a sounder capable of playing sound are disposed in the noise-reducing chamber.
 2. The volute of claim 1, wherein the tongue body is in L-shaped and has a vertical portion and a transverse portion; the volute tongue further comprises two side plates respectively disposed on each side of the tongue body, and a rear plate having a top and a bottom; the top and the bottom of the rear plate are respectively connected to the vertical portion and the transverse portion of the tongue body, and the noise-reducing chamber is enclosed by the two side plates, the rear plate and the L-shaped tongue body; the plurality of holes are defined on the vertical portion of the tongue body, and the sound collector and the sounder both have a front side which faces the rear plate.
 3. The volute of claim 2, wherein a L-shaped air-guiding plate having a vertical portion and a transverse portion is disposed adjacent to the tongue body, the two side plates both extend to the air-guiding plate; the vertical portion of the air-guiding plate and the vertical portion of the tongue body are separated with an interval, which forms a narrow air-guiding passage, the top of the air-guiding passage is in communication with the air outlet, and the transverse portion of the air-guiding plate is connected to the transverse portion of the tongue body; an air-guiding chamber is enclosed by the two side plates, the bottom of the vertical portion of the air-guiding plate, the transverse portion of the air-guiding plate and the vertical portion of the tongue body, the air-guiding chamber is in communication with the air-guiding passage; an opening for allowing the air flow from the air flow chamber to enter into the air-guiding chamber is disposed on the transverse portion of the air-guiding plate.
 4. The volute of claim 3, wherein a movable air-guiding block with a first end and a second end for removably covering the opening is disposed inside the air-guiding chamber, and an adjustment component for controlling the air-guiding block to cover or uncover according to the intensity of the air flow is disposed on the volute tongue.
 5. The volute of claim 4, wherein the adjustment component comprises two pairs of connecting arms, pins and elastic members, each of the elastic members having a first end and a second end; each connecting arm is connected to the first end of the air-guiding block and rotatably connected to the side plate through one pin; the air-guiding block rotates around the pins, and floats upwardly under the impact of the air flow so as to uncover the opening, the second end of the air-guiding block is a free movable end; and the elastic member pushes the air-guiding block to cover the opening.
 6. The volute of claim 5, wherein the elastic member is a spring, the first end and the second end of the elastic member respectively resist against the top of the corresponding connecting arm and the air-guiding plate.
 7. The volute of claim 6, wherein the air-guiding plate has a resisting plane arranged perpendicularly to the spring and is formed on the inner wall of the air-guiding plate above the elastic member, and the second end of the elastic member rests against the resisting plane; and, a recess for receiving the first end of the spring is formed on the top surface of each connecting arm.
 8. The volute of claim 3, wherein the vertical portion of the tongue body has a thickness between 1.5 mm and 2 mm, and the holes have a diameter between 2.3 mm and 3.2 mm.
 9. The volute of claim 2, wherein the volute further comprises an annular volute wall with a first end and a second end, the volute tongue is connected to the first end of the annular volute wall; in the tongue body, the transverse portion is defined as a first cambered section, the vertical portion is defined as a first planar section, and the connecting portion between the transverse portion and the vertical portion is defined as a second cambered section; the first cambered section is arranged closer to an impeller of the centrifugal fan compared to the first planar section, and the bottom surface of the first cambered section serves as a first air-guiding surface of the centrifugal fan; the first planar section is adjacent to the air outlet of the volute, and the outer surface of the first planar section serves as a second air-guiding surface of the centrifugal fan.
 10. The volute of claim 9, wherein the volute further comprises a front cover plate and a rear cover plate, the annular volute wall is connected between the front cover plate and the rear cover plate; an edge of vertical portion is connected to an inner wall of the front cover plate and the rear cover plate, and an edge of the transverse portion is connected to the first endof the annular volute wall and sealed with each other by silicone.
 11. The volute of claim 3, wherein the volute further comprises an annular volute wall with a first end and a second end, the volute tongue is connected to the first end of the annular volute wall; in the tongue body, the transverse portion is defined as a first cambered section, the vertical portion is defined as an upper second planar section and a lower the third cambered section; in the air-guiding plate, the vertical portion is defined as a first planar section, and the connecting portion between the transverse portion and the vertical portion is defined as a second cambered section; the second planar section is arranged closer to the first planar section compared to the first cambered section, the third cambered section is arched toward the air-guiding plate, and is smooth connected to the first cambered section; the first cambered section is arranged close to an impeller of the centrifugal fan, and the bottom surface of the first cambered section serves as a first air-guiding surface of the centrifugal fan; the first planar section is adjacent to the air outlet of the volute, and the outer surface of the first planar section serves as a second air-guiding surface of the centrifugal fan.
 12. The volute of claim 12, wherein the interval at the top of the air-guiding passage is smaller than that of the bottom of the air-guiding passage.
 13. The volute of claim 5, wherein the bottom surface of the air-guiding block is a cambered surface protruding downward, and correspondingly, each wall of the opening on the transverse portion is a cambered surface matching with the bottom surface of the air-guiding block.
 14. The volute of claim 14, wherein the top surface of the air-guiding block is a chambered surface protruding upward, the radian of the top surface is greater than that of bottom surface of the air-guiding block, and the connecting portion between the top surface and the bottom surface is smooth. 